I'm used to seeing proxy attempts for http://mail.yahoo.com/?.intl=us. I
think these are spammers trying to hide the source of their junk.
The above from Jim reminded me that Yahoo is spying on their customers
through the use of what they call "web beacons". The info is at:
http://privacy.yahoo.com/privacy/us under cookies.
Click on "web beacons" . However you can opt-out. If you have
more than one browser, you must opt-out for each browser that you use.